Enhance Depth Perception Research Articles

Enhanced depth perception following high-frequency repetitive transcranial magnetic stimulation of human area V2/V3

Enhanced depth perception following high-frequency repetitive transcranial magnetic stimulation of human area V2/V3

Real-time ambient occlusion and halos with Summed Area Tables

Volume models often show high depth complexity. This poses difficulties to the observer in judging the spatial relationships accurately. Illustrators usually use certain techniques such as improving the shading through shadows, halos, or edge darkening in order to enhance depth perception of certain structures. Both effects are difficult to generate in real-time for volumetric models. Either they may have an important impact in rendering time, or they require precomputation that prevents changing the transfer function interactively, as it determines the occlusions. In this paper we present two methods for the fast generation of ambient occlusion on volumetric models. The first is a screen-space approach that does not require any precomputed data structure. The second is a view independent method that stores volumetric information in the form of a Summed Area Table of the density values, and thus, allows the interactive change of transfer functions on demand, although at the expense of memory space. Despite the fact that similar quality results are obtained with both approaches, the 3D version is more suitable for objects with discontinuous structures such as a vessels tree or the intestines, and it yields better framerates. The screen-space version is more suitable in limited GPU memory environments because it does not need extra 3D texture storage. As an extra result, our screen-space technique also allows for the computation of view dependent, interactively configurable halos using the same data structure. We have also implemented both methods using CUDA and have analyzed their efficiency.

Low Cost Projection Environment for Immersive Gaming

As computer performance and graphics hardware continue to improve, the gamer is increasingly being presented with richer and more realistic visual environments. Viewing these virtual environments is generally still based upon display technology that does not exploit two very important characteristics of our visual system, namely stereoscopic vision that is responsible for the enhanced depth perception we see in the real world and a wide field of view that allows us to sense activity in our far peripheral vision. In what follows it will be argued that for immersive gaming a wide field of view is both functionally more useful and places less stress on the visual system than stereoscopic viewing. In order to support gaming with a wide vertical and horizontal field of view a low cost projection system will be introduced and the implications for game developers discussed.

Enhancing Depth-Perception with Flexible Volumetric Halos

Volumetric data commonly has high depth complexity which makes it difficult to judge spatial relationships accurately. There are many different ways to enhance depth perception, such as shading, contours, and shadows. Artists and illustrators frequently employ halos for this purpose. In this technique, regions surrounding the edges of certain structures are darkened or brightened which makes it easier to judge occlusion. Based on this concept, we present a flexible method for enhancing and highlighting structures of interest using GPU-based direct volume rendering. Our approach uses an interactively defined halo transfer function to classify structures of interest based on data value, direction, and position. A feature-preserving spreading algorithm is applied to distribute seed values to neighboring locations, generating a controllably smooth field of halo intensities. These halo intensities are then mapped to colors and opacities using a halo profile function. Our method can be used to annotate features at interactive frame rates.

A multimodal virtual reality interface for 3D interaction with VTK

The object-oriented visualization Toolkit (VTK) is widely used for scientific visualization. VTK is a visualization library that provides a large number of functions for presenting three-dimensional data. Interaction with the visualized data is controlled with two-dimensional input devices, such as mouse and keyboard. Support for real three-dimensional and multimodal input is non-existent. This paper describes VR-VTK: a multimodal interface to VTK on a virtual environment. Six degree of freedom input devices are used for spatial 3D interaction. They control the 3D widgets that are used to interact with the visualized data. Head tracking is used for camera control. Pedals are used for clutching. Speech input is used for application commands and system control. To address several problems specific for spatial 3D interaction, a number of additional features, such as more complex interaction methods and enhanced depth perception, are discussed. Furthermore, the need for multimodal input to support interaction with the visualization is shown. Two existing VTK applications are ported using VR-VTK to run in a desktop virtual reality system. Informal user experiences are presented.

Using ILIC algorithm for an impressionist effect and stylized virtual environments

Vector fields, often used in science, also find application in the artistic world of sculpture and painting. Apart from color and shape, artists utilize features of direction to depict our natural environment. The line integral convolution (LIC) method, originally developed for imaging vector field in scientific visualization, has the potential to produce images with directional characteristics. In this paper, we present four techniques to explore LIC in generating images in the style of the Impressionists. In particular, we develop an ILIC (Impressionist LIC) algorithm, which takes advantage of the directional information given by a photograph image, incorporates it with a shading technique to blend cool or warm colors into the image, and finally applies the LIC method to imitate artists’ paintings in the Impressionist style. The cool-to-warm blending scheme derives from a painting convention to enhance depth perception. Furthermore, we present a technique using statistical details to control the convolution length for the ILIC algorithm, allowing detailed information to be preserved during the convolution process. We also demonstrate a top-down sampling technique so that a series of mipmaps can be generated to construct virtual environments. These maps, even under multi-resolution viewing, reveal constant strokes, thereby achieving frame coherence in an interactive walkthrough system. The experimental results show satisfactory emulations and efficient computing in fabricating a wide category of artistic virtual environments.

Influence of two-dimensional and three-dimensional imaging on endoscopic bowel suturing.

Several three-dimensional (3-D) video-endoscopic systems have been introduced in surgical practice to enhance depth perception during minimal access surgery (MAS), but the facilitation of endoscopic manipulations by the current 3-D systems remains unproved. The aim of the study was to investigate the influence of 2-D and 3-D imaging modalities on intracorporeal suturing. The standard task consisted of suture closure of 60 mm enterotomies made in porcine small bowel with continuous seromuscular 3/0 Polysorb. Ten experienced surgeons participated in the study. The imaging systems were Storz (2-D), Welch Allyn (3-D), and Zeiss (as both 2-D and 3-D). Each surgeon performed two tasks with each modality in a random sequence. The outcome measures were execution time, suture line leakage pressure, and suture placement score. In addition, the participating surgeons assigned subjective scores on the image quality and the adverse effects of the imaging systems. There was no significant difference in the execution time, leakage pressure, and suture placement score among the various imaging modalities. Depth perception was rated as similar with 2-D and 3-D imaging. Surgeons experienced visual strain with the three systems, but it was rated higher with 3-D imaging. With the current technology, we have not documented any significant difference in task efficiency and quality of endoscopic bowel suturing by trained surgeons between 2-D and 3-D imaging systems.

Randomised study of influence of two-dimensional versus three-dimensional imaging on performance of laparoscopic cholecystectomy

Several three-dimensional video-endoscopic systems have been introduced to enhance depth perception during minimum-access surgery. However, there is no conclusive evidence of benefit, and these systems are more expensive than conventional two-dimensional systems. We undertook a prospective randomised comparison of two-dimensional and three-dimensional imaging in elective laparoscopic cholecystectomy for symptomatic gallstone disease. The operations were done by four specialist registrars as part of their higher surgical training. 60 operations were randomised for execution by either two-dimensional or three-dimensional imaging display (30 by each method). The degree of difficulty of the operation was graded by a consultant surgeon on a standard grading system. The primary endpoints were execution time and the errors made during the procedure. The secondary endpoints were subjective assessment of the image quality and adverse effects on the surgeon. There was no difference between the two-dimensional and three-dimensional display groups in median execution time (3160 [IQR 2735-4335 vs 3100 [2379-3710] s; p = 0.2) or error rate (six vs six). Surgeons reported adverse symptoms immediately after the operations with both systems. The scores for visual strain, headache, and facial discomfort were higher with the three-dimensional system. With the current technology, three-dimensional systems based on sequential imaging show no advantage over two-dimensional systems in the conduct of laparoscopic cholecystectomy.

Developing Technology for Suspended Imaging for Minimal Access Surgery

Some of the problems of performing laparoscopic surgery can be traced to the position and intrinsic qualities of the displayed video image. Conversion of the normal monitor screen image to a suspended image can reduce image-related difficulties. The principles of suspended image production are described and the potential for more flexible image positioning and enhanced depth perception is explained. A recently initiated research program is investigating design possibilities and conducting fundamental research into suspended image appraisal.

Developing Technology for Suspended Imaging for Minimal Access Surgery.

Some of the problems of performing laparoscopic surgery can be traced to the position and intrinsic qualities of the displayed video image. Conversion of the normal monitor screen image to a suspended image can reduce image-related difficulties. The principles of suspended image production are described and the potential for more flexible image positioning and enhanced depth perception is explained. A recently initiated research program is investigating design possibilities and conducting fundamental research into suspended image appraisal.

Genome size, secondary simplification, and the evolution of the brain in salamanders.

Compared to other vertebrates, even including lampreys and hagfishes in some respects, salamanders exhibit a relatively simple organization of brain and sense organs which is illustrated here using the visual system as an example. The greatest simplicity is found in the bolitoglossine salamanders, yet all bolitoglossines possess highly projectile tongues and rely on vision for survival; furthermore, some species are agile and acrobatic. The unusual features of the visual system of salamanders include small numbers of large neurons, a low degree of morphological differentiation among neurons, a small proportion of myelinated axons in the optic nerve, and an optic tectum consisting essentially of a periventricular cellular layer and a superficial fiber layer. Similar features are found throughout the central nervous system of salamanders and in the lateral line, auditory and olfactory systems as well. Phylogenetic analysis shows that the most parsimonious interpretation of these data is that the simple organization of the brain and sense organs of salamanders was derived secondarily from a more complex ancestral state. We hypothesize that increased genome size has led to simplification of the nervous system in salamanders. Increased genome size appears to have had profound effects on neural development in salamanders, leading to paedomorphosis, the retention of juvenile or even embryonic characteristics into adulthood. In particular, large genome size is associated with large cell size and reduced rates of cell proliferation, migration and differentiation. Secondary simplification has constrained the function of the salamanders' visual system, primarily by increasing cell size and decreasing cell numbers. However, it also has provided an opportunity for the evolution of compensating mechanisms, which have helped to restore or even enhance visual function. Most apparent among the compensatory mechanisms of bolitoglossine salamanders is the presence of well developed ipsilateral retinotectal projections, which apparently enhance depth perception. It is difficult to explain the unusual history of the nervous system in salamanders solely in terms of natural selection and adaptation. Increasing genome size through selfish replication appears to have played a major role in the evolution of salamander brains by imposing functional constraints as well as creating opportunities for overcoming them.

Three-dimensional video imaging for endoscopic surgery

Recently a number of manufacturers have developed three-dimensional (3-D) video systems which significantly improve visualization and enhance the ability of the surgeon to perform delicate endoscopic dissection and suturing. These 3-D video systems may also improve the education of surgeons-in-training as they would have a better understanding of three-dimensional anatomy during laparoscopic surgery. Most of the 3-dimensional stereoendoscopic video systems currently available have four basic principles of stereoendoscopic image processing in common: image capture, conversion of 60–120Hz images; presentation of left and right images on a single monitor; and separation of the left and right eye images. Skill tests performed assessing laparoscopic suturing and knot tying have demonstrated a 25% increase in speed and accuracy of these laparoscopic tasks when utilizing a three-dimensional video system as compared to a standard two-dimensional endoscopic video system. We believe that three-dimensional video imaging greatly facilitates the efficiency of endoscopic reconstructive procedures. While three-dimensional video imaging systems are more costly than conventional two-dimensional video equipment, the enhanced depth perception produced by 3-D endoscopes has been demonstrated to improve the performance of minimally invasive surgical procedures.

Hypnosis, depth perception and schizophrenia.

A series of experiments with a single S on the effects of post-hypnotically altered perception on behavior suggests a relation between a schizophrenic-like condition and loss of depth perception, and a psychedelic state with enhanced depth perception. These changes were not observed with blurred vision or enhanced visual clarity.